1. Field of the Invention
The present invention relates to an actuator, an optical fiber moving apparatus driven by the actuator and an optical switch driven by the actuator, and more particularly, to an actuator having a rough moving means using a linear motor mechanism and a micro moving means using a thrust force obtained by converting electric energy into kinetic energy.
2. Description of the Related Art
Conventionally, there are known an actuator for executing inchworm operation and an actuator driven by impact drive by using, for example, a piezoelectric element, as actuators for obtaining a thrust force by converting electric energy into kinetic energy.
The operation principle of the inchworm operation will be described here with reference to FIG. 18. An inchworm mechanism, which is composed of bodies 41 and 42 and piezoelectric elements 43-1 to 43-3 extendable in two-axes directions, is placed on a slide surface 44 (FIG. 18(a)). First, the piezoelectric element 43-1 extends in an upward direction orthogonal to a traveling direction by the voltage applied thereto, thereby the body 41 is lifted upward (FIG. 18(b)). Next, the piezoelectric element 43-2 extends in the traveling direction by the voltage applied thereto (FIG. 18(c)). After the piezoelectric element 43-2 extends to its full length, only the voltage applied to the piezoelectric element 43-1, which has extended upward, is shut off, and the body 42, which has been lifted upward, returns onto the slide surface 44 (FIG. 18(d)).
Next, the piezoelectric element 43-3 is extended in the upward direction orthogonal to the traveling direction by the voltage applied thereto, and the body 41 is lifted upward thereby (FIG. 18(e)). The voltage applied to the piezoelectric element 43-2, which has extended in the traveling direction, is shut off, and the piezoelectric element 43-2 returns to its original length (FIG. 18(f)). Finally, the voltage applied to the piezoelectric element 43-3 is shut off, and the body 41, which has been lifted upward, returns onto the slide surface 44 (FIG. 18(g)). As a result, the bodies 41 and 42 moves forward in the traveling direction by the amount of expansion of the piezoelectric element 43-2.
The bodies 41 and 42 can be moved in an opposite direction by applying a voltage to the piezoelectric elements 43-1 and 43-2 in a reverse sequence.
Further, there is an impact drive mechanism acting as a micro actuator mechanism, in addition to the above inchworm mechanism. The operation principle of the impact drive mechanism will be also described with reference to FIG. 19. The impact drive mechanism is arranged such that a body 51 is joined to a body 52 through a piezoelectric element 53. The body 51 is pressed against a slide surface 54 by the pressure force F applied thereto (FIG. 19(a)). When the piezoelectric element 53 is extended as shown in the figure by the voltage abruptly applied thereto, the body 51 begins to slide left on the slide surface 54 because the inertial force of the body 51 overcomes the friction between the body 51 and the slide surface 54. At the same time, the body 52 also moves right on the slide surface (FIG. 19(b)). Next, when the voltage applied to the piezoelectric element 53 is slowly released, the piezoelectric element 53 slowly returns to its original length. At this time, almost no inertial force is caused to both the bodies 51 and 52 because they have a small acceleration. Accordingly, the movement of the body 51 is prevented by the frictional force generated by the pressure force F between the body 51 and the slide surface 54. As a result, the amount of movement of the impact drive mechanism, which was made when the piezoelectric element 53 extended at the beginning, is maintained, and the overall shape thereof returns to its original shape (FIG. 19(c)). The repetition of this operation permits the impact drive mechanism to move in the direction of the body 51.
The impact drive mechanism can be moved in an opposite direction by slowly extending the piezoelectric element 53 at the beginning and then by abruptly contracting it when it extends to its full length.
The actuator disclosed in Japanese Unexamined Patent Publication (KOKAI) No. 4-360025 is known as an actuator using the above inchworm mechanism, and the actuator disclosed in Japanese Unexamined Patent Publication (KOKAI) No. 8-266073 is known as a conventional technology using the above impact drive mechanism.
A first problem of conventional actuators resides in that they cannot move a large distance at high velocity. This is because that only an inchworm mechanism and an impact drive mechanism are mounted thereon and these mechanisms are driven making use of the micro displacement of a piezoelectric element. That is, this type of the conventional actuators are arranged as an actuator specialized in micro drive and cannot move a large distance at high velocity.
A second problem of the conventional actuators resides in that they cannot be formed in a small size. This is because that when a conventional actuator is composed of only the micro actuators such as the inchworm mechanism and the impact drive mechanism, it is impossible to move it a long distance at high velocity. To cope with this problem, it is necessary to separately provide a high velocity drive mechanism such as a voice coil motor on the high velocity drive mechanism. As a result, the overall size of the conventional actuator is increased.
Therefore, when a mechanical type optical switch is composed of an optical fiber moving body using a conventional actuator, switching cannot be carried out at high velocity or a compact optical switch cannot be realized.